Integrated Pest Management Manual

Ants

This module is intended to serve as a source of basic information needed
to implement an Integrated Pest Management program for structure-infesting
ants. Any pest management plan or activity must be formulated within the
framework of the management zones where it will be implemented. Full consideration
must be given to threatened and endangered species, natural and cultural
resources, human health and safety, and the legal mandates of the individual
parks. Recommendations in this module must be evaluated and applied in
relation to these broader considerations.

Ants are among the most successful insects. Experts estimate that there
could be 20,000 or more species of ants in the world. They have evolved
to fill a variety of different ecological niches as predators, herbivores,
leaf-cutters, seed-harvesters, aphid- tenders, and fungus-growers. They
are found in deserts and rainforests, mountains and valleys, from the
Arctic Circle to the tip of South America. They are interesting organisms
that should be studied to better understand their unique behaviors and
their roles in the earth's ecosystems.

They can also be pests, however. Fire ants and others may sting or
bite people and animals. Pharaoh ants get into wounds and dressings
in hospitals. House-infesting ants can become pests by their presence
in kitchens and living areas. Carpenter ants tunnel into structural
wood. Mound-building ants mar the appearance of lawns and landscaped
areas. Sometimes ants must be managed to suppress a pest problem.

IDENTIFICATION AND BIOLOGY OF ANTS

Only a comparatively small proportion of ant species are damaging
and require control. For National Park Service personnel, the ants most
often of concern will be species in three groups: fire ants, carpenter
ants, and house-infesting nuisance ants. The first two are discussed
in separate Integrated Pest Management modules. This module addresses
the third group, house-infesting ants--those ants that most commonly
invade structures looking for food, water, or nesting sites.

A detailed description of every pest ant is beyond the scope of this
module. Well over a dozen are considered common pests of structures,
and many others are occasional pests. The species most likely encountered
will depend on geographic location and surrounding habitat. Detailed
information on identification, biology, and management of specific pest
ants should be obtained from the local Cooperative Extension Service,
your regional National Park Service Integrated Pest Management coordinator,
or from the References listed at the end of this module. A table that
lists key features used to identify major pest species of ants follows.

Species

Worker size

Color

Thorax shape

No. of nodes

Other id characteristics

Treatment

Bait

Pavement ant

3/16"

dark brown

uneven

two

Grooves on head and thorax. Stinger at tip of abdomen.

barrier-poor
nest-excellent

sweet

Thief ant

1/32"

yellow

uneven

two

Stinger at tip of abdomen

barrier-poor

sweet or protein

Crazy ant

1/8"

dark brown

uneven

one

Very long legs. First antennal segment twice as long as head.

barrier-good

nest-excellent

sweet or protein

Field ant

3/18"

brown to very dark brown

uneven

one

none

barrier-excellent

sweet

Pharoh ant

1/16"

yellow with red abdomen

uneven

two

none

barrier-poor

sweet or protein

Argentine ant

1/8"

brown; sometimes light brown

uneven

one

sparse body hairs; no hairs on thorax

barrier-poor

sweet

The Ant Colony and Life Cycle

Ants belong to the insect order Hymenoptera, which also includes the
wasps and bees. Ants are distinguished from many of their nearest relatives
by two characteristics: a narrow "waist" (the slender free-moving
portion of the abdomen called a (pedicel) and elbowed antennae.

Ants also differ from most other insects in that they are social, similar
to termites and certain bees and wasps. This means that ants live in large
cooperative groups called colonies. Two or more generations overlap in
the colony; adults take care of the young and are divided into castes,
specialized groups that take care of certain tasks. Ants have reproductive
castes, the queens and males, and nonreproductive castes, the workers.

Queens. A queen is generally the largest individual in the colony.
She has wings until after her mating flight, when she removes them. The
primary function of the queen is reproduction, but after establishing
a new nest she may also care for and feed the first brood of workers.
Once she has produced her first brood, she becomes an "egg-laying
machine," cleaned and fed by her offspring. She may live for many
years until replaced by a daughter queen. Some ant species have more than
one queen in the nest.

Males. Male ants are generally winged and usually keep their wings
until death. Apparently, the male ant's only function is to mate with
the queen. Once he does, he dies, generally within two weeks. Males are
produced in old, mature colonies.

Workers. The workers are sterile, wingless females who build and
repair the nest, care for the brood, defend the nest, and feed both immature
and adult ants, including the queen. There may be workers and soldiers
of different sizes that specialize in certain tasks.

Ants develop through a complete life cycle of egg, larva, pupa, and adult.
The egg is tiny, almost microscopic in size. The larva is legless and
grub-like, very soft and whitish in color. It is also helpless and depends
totally on workers for food and care. The pupa looks somewhat like the
adult but is soft, unpigmented, and cannot move around. Some are enclosed
in a cocoon, some are not. A newly-emerged adult requires several days
for its body to harden and darken.

New Colony Formation
Once a colony of ants matures, it can establish new colonies through various
methods, depending on the species. The two most common are budding and
swarming. The appropriate management strategy depends on how a colony
spreads, so it is essential to correctly identify the ant species before
deciding how to manage it.

Budding. Budding is the breakaway of a group of ants from a mature
colony to form a new colony. The group usually consists of one or more
queens and some workers carrying larvae. Budding is common with species
of ants that have multiple queens, such as Pharaoh ants and Argentine
ants. Residual insecticides should not be used for ants that undergo
budding because they can stimulate this process.

Swarming. Most ants establish new colonies through swarming. Every
now and then, particularly in spring or early summer, mature ant colonies
generate large numbers of winged forms. These are the young queens and
males, going off to mate. An inseminated queen then rids herself of her
wings and attempts to start a new nest in a cavity, under a stone or a
piece of bark, or by excavating a hole in the ground. She rears her first
brood alone, feeding them with salivary secretions and infertile eggs.
If successful, the first brood opens up the nest and brings in food for
themselves, the queen, and subsequent broods, and the colony grows. However,
the percentage of queens that successfully begin new colonies is thought
to be very small.

The Difference Between Winged Ants and Winged Termites Although ants and termites are very different, they are often confused.
They are alike in that they live in colonies and periodically swarm. Swarming
forms of both are dark and winged. But worker termites are whitish and
never seen running freely about as do ants. Instead, termites remain protected
in their nests and galleries in wood and soil.

Winged adult ants can be told from winged termites by the following differences.
Winged ants have a narrow waist, front wings that are larger than the
rear, and elbowed antennae. Winged termites have a fat waist, equally
sized wings, and straight, beaded antennae.

Seasonal Abundance Most outdoor ants increase in population and activity from spring
into summer months and then decline from fall into early winter as the
temperature drops and the ants' natural food supplies dwindle. Other ants,
such as the Argentine ant, may increase in numbers in the fall as various
colonies aggregate together to overwinter. Some ants, such as the Pharaoh
ant, which may live entirely indoors, exhibit little seasonality.

Feeding Habits Knowing the food habits of the particular ant species is important
in ant management because it may enable the location and elimination of
the food that is attracting the ants to the site, it can help to locate
foraging trails to track the ants back to their nest, and it can help
to choose an effective bait.

Ants feed on many different types of food. Some species will feed on practically
anything; others may limit their food to a narrow range. Ants infesting
structures are typically feeding on "people food," both food
in storage (sugar, cakes, cookies, breakfast cereals, etc.) and food from
spills and garbage. But they may also be preying on other insects or scavenging
on dead insects in windows or lights.

Food preferences are often seasonal. When the queen is actively laying
eggs, worker ants typically gather protein- based foods for the queen.
At other times they may ignore protein foods completely and restrict their
foraging to sugars and greases.

Many ants obtain sugar by feeding on honeydew, a sweet substance secreted
by aphids and other plant-sucking insects. They often defend these insects
from predators and tend them as if they were their personal food supply.
Indoor infestations of ants are occasionally traced to large populations
of aphids on outdoor foundation plants or indoor houseplants.

The six most common ant species that infest buildings are the pavement
ant, the thief ant, the crazy ant, the field ant, the Pharaoh ant, and
the Argentine ant.

Pavement Ant Identification and Biology

Pavement ants (Tetramorium caespitum) were introduced to the
United States from Europe and occur throughout the eastern United States.
They are an important pest in the Midwest and New England. These are small
ants, about 3/16" long, and are dark brown in color. They build nests
along sidewalks, building foundations, and under stones, boards, bricks,
and mulch or leaf piles. These ants readily make trails to and from food
sources and often forage along the edge of carpeting or baseboards. They
are also common around the base of toilets. They often nest in protected
areas so the nests may be hard to locate, but this is essential to manage
infestations of this species. There can be several thousand in a colony.

Pavement ants feed on a wide variety of foods including other insects,
greasy foods, and plants. While they are often found in damp areas, lack
of moisture does not limit their development, so solving moisture problems
alone will not affect these ants. Vegetation-free borders should be installed
around buildings, and any cracks in building foundations should be sealed.
Any loose material under that could provide nesting habitats and should
be raised off the ground.

Thief Ant Identification and Biology

The native thief ant (Solenopsis molesta) is found throughout
the United States, but primarily in the eastern and central states. A
very small ant, thief ants are easily confused with the Pharaoh ant. The
best way to tell them apart is to look at the club on the end of the antenna
with a magnifying glass and count the number of segments; thief ants have
two segments, while Pharaoh ants have three. Thief ants are named for
their habit of stealing food from the nests of other ants. They nest outside
under debris, rocks, or logs; indoors they nest in wall voids and behind
baseboards. They are very small and can easily enter packaged foods, so
food should be enclosed in tightly-sealed containers. Locating thief ants'
nests can be difficult and time-consuming because their small size can
make it difficult to follow the trail. Thief ants feed on both protein
and sweets and will tend aphids, mealybugs, and scales to obtain the honeydew
they excrete.

All cracks in walls should be sealed to keep these ants from entering
buildings. Patience is essential in managing the ants because the nest
can be so hard to locate. Baits do not seem to be effective for thief
ants since they tend not to eat enough bait to bring sufficient quantities
back to the nest for it to work.

Crazy Ant Identification and Biology

Crazy ants (Paratrechina longicornis) were introduced to the
United States from India. Their distribution is limited to the Gulf coast
from Florida to Texas. They are easily identified by their long legs and
their habit of erratically moving from place to place (hence the name
"crazy"). Crazy ant trails are not readily obvious because of
this erratic movement. The easiest way to find the nest is to look for
workers carrying pieces of food or workers with swollen abdomens. These
ants are carrying food back to the nest. By observing their movement,
it should be possible to find the nest. Crazy ants are highly adaptable
and will nest in a variety of locations, from very dry to moist. They
will nest under objects, in rotten wood or trash, in tree cavities, as
well as in debris left standing in buildings for long periods of time.

These ants feed on a variety of foods including grease, sweets, and other
insects. In some areas they are considered a biological control agent
for houseflies. They also tend aphids and scales to feed on their honeydew.
While crazy ants need moisture, elimination of water by itself will not
get rid of these ants since they can survive under a wide range of conditions.
Elimination of food sources and nest sites are equally important in the
management of this ant.

Crazy ants do not respond well to baits, so they cannot be relied upon
for management of this ant. Surrounding buildings with vegetation-free
barriers such as stone or brick (but not wood mulch) will keep ants from
entering buildings to nest.

Field Ant Identification and Biology

Field ants (Formica spp.) are found throughout the United States
but primarily in the Midwest and North. They are large (3/8" long)
and dark brown to black. They are often confused with the carpenter ant,
but can be distinguished by an uneven thorax (see ant identification chart
at the end of this module). Field ants feed on other insects as well as
insect honeydew. They cause concern because they usually nest near structures
and are often mistaken for carpenter ants. Nests are often made in grassy
areas and can be difficult to see because they are low to the ground.
Field ants will also nest in leaf litter or mulch that is more than two
inches thick, and can live under stones, firewood, or other debris that
might be found in a lawn area. If pesticide drenches of mounds are used
to manage this insect it should be remembered that they will be slow to
act because it often takes foraging ants days to return to the nest.

Pharaoh Ant Identification and Biology

Pharaoh ants, (Monomorium pharaonis), are small yellow ants
about 1/16" long. They are easily confused with thief ants, also
a small yellow ant. To distinguish the two, it is necessary to look at
the antennae. Pharaoh ants have twelve segments with a three-segmented
club on the end, while thief ants have ten segments with a two-segmented
club. Pharoah ants are native to tropical Africa but are now distributed
throughout the world. They are usually associated with heated buildings
since they cannot survive outside year round in the majority of the United
States. These ants will nest in any dark void in a structure as well as
in folded bags or newspapers. In the subtropical United States they will
nest outside in leaf litter, piles of bricks, potted plants, or under
roof shingles.

Pharaoh ant colonies can become quite large, often containing as many
as 300,000 workers with several queens. New colonies are formed by budding,
when some of the workers, brood, and a few queens move to a new location.
In warm areas where they can survive outdoors they will move from building
to building.

Pharaoh ant management is more dependant on locating areas of ant activity
than eliminating the colony, since they are so large and can spread so
easily. Place jelly baits on 1" squares of paper or tape and place
in damp, dark areas. These ants move along electrical wires, so an inspection
should include areas where wires enter walls or appliances, as well as
behind switchplates and outlets. Pharoah ants will also nest in and around
appliances such as refrigerators or stoves that have food or water around
them. A useful tool for the management of this ant is to make a map of
the site and mark locations where ants and their colonies are found. This
will help to identify new areas of activity over time.

Sanitation is essential for Pharaoh ant management, since elimination
of food sources will make them more receptive to insecticide baits. Residual
insecticides should not be used for Pharaoh ant management. They can repel
ants, forcing more colonies to form through budding while killing only
a small number of ants. During the first two to four weeks of the program,
place baits containing an insect growth regulator and a food attractant
inside a soda straw throughout the area of infestation. These should be
located along edges and in corners where ants are most likely to encounter
them. Placing baits inside straws will keep them fresh and away from people
and domestic animals. Replace these with boric acid/food attractant baits.
One food bait is three parts honey: two parts peanut butter: one part
mint apple jelly : one part egg yolk baby food. Commercial baits are also
available. Exterior treatments may be necessary in subtropical areas of
the United States or during the warmer months in northern areas. Remember
that both insect growth regulators and boric acid are EPA- registered
pesticides, so your regional National Park Service Integrated Pest Management
coordinator should be consulted before using these materials.

Argentine Ant Identification and Biology

Argentine ants, (Iridomyrmex humilis), are an imported species
common throughout the southeast and southern California. These ants will
nest in soil and mulch, as well as under stones, logs, and debris. They
are often found in tree holes, bird nests, leaf litter, and bee hives.
These ants form large colonies; workers from different colonies do not
fight and will often join together to form larger colonies. This means
that areas from which colonies are eliminated can quickly be repopulated.
These large colonies will often split by budding during the warmer months.
Although Argentine ants form winged reproductives, they do not swarm.
They feed on a variety of foods but seem to prefer sweets and will feed
on aphid honeydew. They will even feed on fruit crops and are considered
an agricultural pest in some areas.

Argentine ant trails are easy to locate along sidewalks, foundations,
and along the edges of buildings. If grass grows to the edge of the building
it should be pulled back during an inspection. These ants will also move
into buildings by climbing up trees onto wires entering buildings, so
any place where branches touch buildings should be inspected as well.
As with so many other ants, use of a vegetation-free border and correction
of moisture problems will help in management of Argentine ants. Insecticide
baits are useful for managing this ant.

MONITORING AND THRESHOLDS

Identification of the species will help to determine where the nest
might be located, what the ants might be feeding on, and the best tactics
for control. All parts of the building and the surrounding area should
be inspected for ant activity as well as food and water sites. People
that work in the building might have seen the ants also. Some species
are most active in the evening. For these, a daytime inspection might
discover little, while significant ant activity might be observed at midnight.

Some infestations may require an intensive survey program using nontoxic
baits to determine likely nesting sites. Good baits are jelly, honey,
peanut butter, bacon grease, or raw liver. The baits (or a combination
of baits) should be placed on small pieces of cardboard, aluminum foil,
masking tape, or plastic pill bottle lids throughout the building and
periodically checked for feeding ants. Active sites should be noted on
a survey diagram. Baits that haven't had any feeding activity in 24 hours
should be moved. Over a period of days the survey diagram will pinpoint
areas of activity. In addition, trails of ants feeding on the bait can
sometimes be followed back to the nest site.

There is no single threshold level for house-infesting ants. Threshold
levels need to be set separately for each site. For example, a single
ant in a first-aid station may be one too many. In an eating area, control
actions might be initiated if there were more than a half-dozen ants in
a day, while most people's tolerance for ants in a rustic and open recreation
room would likely be much higher.

NON-CHEMICAL CONTROL OF ANTS

The most effective ant control results from the destruction of the
queens and the nest itself. If the nest is found by tracking workers,
or through a survey, eliminating that nest is fairly simple, particularly
if it is located, as it often is, outdoors, or in the soil beneath a cracked
floor. It is simply a matter of mechanically destroying the nest.

But effective ant management is rarely that simple. Sometimes you can't
find the nest. Often there are multiple nests. (One species, the Pharaoh
ant, can have hundreds of small nests within a single room.) There may
be a constant pressure from ant colonies invading from surrounding areas.
In most cases, long-term management of pest ants means integrating improved
sanitation, structural repairs, and habitat modification along with one
or more direct control tactics such as insecticide baits, crack and crevice
treatments, and direct physical controls.Successful ant management usually requires a combination of management
tactics, ranging from caulking to cleanup, improved sanitation to habitat
modification, as well as targeted and limited insecticide treatment.

The keys to success in ant management are, first, vigorous inspection
to determine the nature and extent of the infestation, and, if at all
possible, the location of the nest. Second, meticulous sanitation to eliminate
readily available food and water. Third, the choice of the right combination
of tools to eliminate the problem. The listing for each ant species provides
more information on management strategies relevant to that ant.

Improved Sanitation Like all pests, ants need food, water, and shelter to survive. By
limiting these three essentials, you make it more difficult for ants to
live in the infested area. Simply by improving sanitation you can often
suppress existing populations and discourage new invasions.

Ants can enter many types of food packaging, particularly once the package
has been opened. (They have even been found inside glass jars after traveling
around the threads of a screw-on lid!) Cereals, sugar, and other bulk
food should be stored in plastic containers with snap-on lids, in glass
jars with rubber seals, or in a refrigerator.

Food spills also feed ants. As with cockroaches, enthusiastic cleaning
helps to minimize ants. Frequent vacuuming, sweeping, or mopping of floors
and washing of counter and table tops eliminates much of the food ants
may be foraging on. Trash should be stored away from infested areas and
monitored for spills.

Ants can get their water from many sources inside a structure: condensation
on pipes and air conditioners, leaky plumbing, aquariums, pet dishes,
houseplant containers, floor drains, etc., and limiting these is rarely
practical.

Ant-Proofing Ants can enter and move through a structure through innumerable tiny
cracks and openings. Yet caulking and otherwise sealing cracks and crevices
being used by ants can often have great effect in suppressing the population.
Many easy-to-use and effective silicon sealers and expandable caulk products
have been recently developed, including some designed specifically for
pest management. Repairing torn screens and installing doorsweeps can
also prevent ants from easily entering a structure. Non-vegetation barriers
such as stones or brick walkways next to a building can be helpful in
helping to keep ants out of structures as well.

Habitat Modification
Trim the branches of trees located close to structures so the branches
do not act as runways from nest sites to roof or siding. Alter landscaping
to minimize the number of aphids and other honeydew-producing insects
that attract ants. Firewood kept indoors should be moved outdoors or regularly
inspected for ants. Don't stack wood next to structures and move trash,
since ants often nest under objects. Moisture accumulation in buildings
can also result in ant infestations.

Direct Physical Control Ants can be discouraged from foraging in certain limited sites with
sticky barriers. For example, commercially available sticky repellents
or petroleum jelly can be applied in a narrow band around table legs to
prevent ants from walking up to the tabletop. Double-sided tape can also
be used.

Large numbers of worker ants can be mopped or sponged up with soapy water.
Water, especially boiling water, has also been used to flood ant nests.
Some ground-ant nests have been destroyed by digging them up and destroying
the nest structure.

CHEMICAL CONTROL OF ANTS

Many people, on discovering ants, simply spray insecticide wherever
they have seen ants. This is a poor strategy, usually doomed to failure.
Applying undirected, general insecticide sprays indoors is unsatisfactory
because the sprays only "harvest" a small portion of the workers
and have little effect on the colony, the ultimate source of the problem.
A further problem is that some species are apparently triggered into "budding"
new colonies when they contact insecticide near their nests and foraging
sites.

The chemical tools available for ant control have changed in the past
few years with the addition of insect growth regulators, new baits, and
commercial bait stations, and new tools can be expected in the future.
Even so, insecticides are only one of the tools available for control
of ants, and not always the best or most important. Ant biology should
be considered when deciding whether or not to use insecticides. For example,
insecticides are often not effective against mound ants because it often
takes foraging ants several days to return to the nests. Consult your
regional National Park Service Integrated Pest Management coordinator
for information on using pesticides as part of an ant management program.

Ant baits. The best baits for ants are those whose toxicant kills
ants slowly. In this way, worker ants live long enough to take the baits
back to the nest and feed it to the colony and queen. A number of baits
are now available. Some are prepackaged in child-resistant bait stations.
Some are gels or pastes designed to be placed in small pea-shaped amounts
throughout an area. Some products (such as boric acid) are designed to
be mixed with a food. Bait products typically will work against certain
species of ants but not against others, so it is important to check the
label to make sure the ant you wish to control is listed.

Insect growth regulators (IGRs). These are available in bait form
for some ant species. Insect growth regulators inhibit normal development
of insects. They are slow-acting because they stop the next generation
from developing rather than killing the current generation. A recent study
comparing the insect growth regulator fenoxycarb to a commercial bait
found that the growth regulator was more effective than the bait in eliminating
Pharaoh ants. This is most likely because the bait kills ants too quickly
to be effectively distributed throughout the colony (Williams and Vail
1994). Crazy ants do not seem to respond well to bait, and baits may be
slow-acting against field ants since they often stay away from the nest
for several days.

Liquid and aerosol insecticides. Nearly all of the insecticides
labeled for use against cockroaches are also labeled for use against ants.
These insecticides are most effective when used to treat actual nest sites.
Insecticides are less effective, but still may provide acceptable results
when used to treat inside cracks and crevices used by ants in and around
infested sites. They are least effective, as well as offering the highest
potential of human exposure, when they are simply applied to sites where
activity has been observed.

Drenches. For certain ground-nesting ants that dig deep nests outdoors,
a soil drench or mound drench can be effective where other treatments
are not. As its name implies, a soil drench consists of applying enough
insecticide dilution directly to a mound or nest so that the entire nest
is drenched.

Dusts. Dusts may also be used on occasion for ant control if they
are used lightly or directed into nests. In large amounts, dusts tend
to repel ants. But they have the advantage of floating back through wall
voids to reach nests that may not be accessible with other formulations.

Granules. Granules are rarely used in household ant control. They
may be useful, however, when a lawn or field is heavily infested with
many colonies of a shallow, ground- nesting species of ant.

REFERENCES

1. Williams, D.F., and K.M. Vail. 1994. Control of a natural infestation
of the Pharoah ant (Hymenoptera: Formicidae) with a corn grit bait of
fenoxycarb. Jrnl. of Econ. Entomol. 87(1): 108-115.